First, you should understand the management.
W and S keys switch speed forward and backward. Your Marine "speedometer" is located at the left edge of the screen. There is a small course, the usual course and complete the course. The same is the case with the movement back.
Q and E keys are lowered and raised the ship at a depth accordingly! Remember this!
Also where the mouse cursor is looking in the game, the ship will sail in this direction.
Quest "Bar of divers"
Click on V. When you see the corresponding label, you need to click on Jack. Talk to him. Swim forward, until you see the first station - it's a bar. Close to him, and when you see the inscription, you need to press the R key to moor.
Quest "About Hassli"
You need to talk with the long-haired guy in the bar to learn about the engineer Hassli. Talk with everyone, including Jack.
Quest "First Sailor"
You must hear from Jack that you need to move to the west. Also you need to find the first sailor. There is a picture at the top of the bar, with which you can interact. Click on it to get the booty. Take all that is in the secret niche.
Swim down the only possible way! Swim past the mines. Soon you will see a prison. Moor to it and talk with Kate, the girl in the chamber. During the conversation, Kate will escape from the chamber. Quickly get out from the prison. Take part in the first battle. Shoot the enemy, aim by the cursor on the screen and press the left mouse button.